The present invention relates to a regenerative gas turbine with a heat exchanger.
As shown in JP-U 60-6986 and JP-U 61-18384, a regenerative gas turbine engine has a heat exchanger including a rotary heat exchange core disc wherein thermal energy from a high temperature exhaust gas from a turbine is used to heat a compressed discharge air from a compressor. In the heat exchanger, it is necessary to separate in a seal tight manner a flow of high temperature exhaust gas admitted to a portion of the heat exchange core disc from a flow of compressed air having passed through another portion of the heat exchange core disc. It has been the common practice to seal, between an axial face of the heat exchange core disc and a substantially planar platform of a duct housing. If this seal is broken owing to thermal deformation of the platform, a gas leakage takes place, resulting in a drop in heat exchange effeciency.
A two-shaft regenerative gas turbine called "AGT 100" is known according to a published leaflet "DDA/GM NASA Contract No. DEN3-168, 1981." In this gas turbine, a good gas sealing performance is exibited owing to a platform with an integral high temperature exhaust gas duct housing. This platform-duct integral structure is made of a material with a low thermal expansion, i.e., Litium Aluminium Silicate, and has a straight cross bar portion separating the exhaust gas from the compressed air having past through the core disc. After a prolonged use, this cross bar portion becomes excessively high in temperature as compared to its peripheral portion that is relatively low in temperature. Thus, even if the low thermal expansion material is used, there is possibility that the surface of the platform becomes rough and degraded, and at the fatal case the surface is damaged owing to thermal stress. Besides, the platform-duct integral structure is not easy to handle in assembly owing to its bulky size, causing a poor yield in manufacture.
An object of the present invention is to improve a heat exchanger for a gas turbine such that a good sealing performance is maintained between a platform and a heat exchange core disc without using the bulky integral structure mentioned above.